1. Field of the Invention
The present invention relates to a liquid ejection apparatus, an image forming apparatus and a liquid ejection method, and more particularly, to a liquid ejection apparatus and a liquid ejection method whereby an ejection liquid can be ejected stably by securing gas barrier properties and preventing aggregation or sedimentation of the coloring material, or the like, contained in the ejection liquid.
2. Description of the Related Art
Japanese Patent Application Publication No. 2005-041048 discloses a liquid spraying apparatus which is mainly constituted of a recording head 222, an ink cartridge 221, a pressure control unit 223, as shown in FIG. 15. The ink cartridge 221 is connected with a pump 238 in the pressure control unit 223 via a pressure control valve 229 by means of a pressure control tube 237. The pressure sensor 236, which is connected with the ink cartridge 221 via the pressure control tube 237, measures an air pressure in the ink cartridge 221.
By means of this composition, it is possible to keep the air pressure in the ink cartridge 221, in which an ink bag 231 is accommodated, to a negative pressure, by means of a control circuit 239 in the pressure control unit 223 controlling the pressure control valve 229 and the pump 238 on the basis of a determination signal from the pressure sensor 236.
However, in Japanese Patent Application Publication No. 2005-041048, the ink bag 231 is composed of a member having plastic properties and gas barrier properties. More specifically, for example, the ink bag is composed of an aluminum laminate film in which an aluminum film is interposed between an outer film (a nylon film) and an inner film (a polyethylene film).
Therefore, the ink bag 231 has a thickness of several 100 μm and has relatively high rigidity, and consequently, local creasing or wrinkling occurs as the ink is consumed. If the local creasing or wrinkling occurs in the ink bag 231, then the convection flow in the ink liquid (i.e., ejection liquid) stagnates in the corresponding portion, and there is a possibility that aggregation or sedimentation of the coloring material, or the like, contained in the ink liquid will occur. If the aggregate or sediment caused by the aggregation or sedimentation of the coloring material, or the like, flows into the recording head during ejection of the ink, then ejection failure will arise.
Another composition is possible in which the ink bag 231 is provided with folds in the form of a three-dimensional folding composition or accordion structure, but in this case also, convection flow of the ink in the region of the fold is prevented, and consequently, aggregated material and sediment of the ink is generated, and this aggregate and sediment is supplied to the recording head, giving rise to pressure loss and blockages of nozzles.